Extended Data Fig. 8: High-frequency capacitance characterization of ultrathin HZO.
From: Enhanced ferroelectricity in ultrathin films grown directly on silicon
a, Schematic heterostructure of ultrathin HZO on metallic TiN probed the microwave capacitance measurements to eliminate contributions from the semiconducting Si substrate. b, PFM phase contrast (left) and topography (right) imaging for 10 cycles HZO on TiN-buffered Si. Ultrathin ferroelectricity persists on top of metallic underlayers as well as dielectric SiO2, although the topography is rougher than the films on SiO2 due to the inhomogeneity introduced by the sputtered TiN. c, SCM dC–dV spectroscopy loops taken on multiple bare regions of an ultrathin ten-cycle HZO film, demonstrating reproducible SCM response. The square 180° phase hysteresis and dC/dV loops, which integrates into the classic butterfly-shaped capacitance–voltage plot (Fig. 2c), provides conclusive evidence of ferroelectric polarization switching beyond PFM loops (Fig. 2e, Extended Data Fig. 6). The microwave-frequency nature of the SCM enables leakage-mitigated differential capacitance measurements of ultrathin films (Methods). d, PFM switching-spectroscopy loops taken on the same region of the ten-cycle HZO as the SCM measurements, confirming the ferroelectric-like phase and amplitude hysteresis. We note that the SCM and PFM switching spectroscopy was done using the Asylum Cypher scanning probe microscope at Asylum Research (Methods).
